As known, spectacles are optical devices consisting of a pair of lenses made of transparent material, and of a support frame, traditionally called “spectacles frame”, which is structured so as to stably hold the lenses, and to position the above mentioned lenses in front of the user eyes when the user wears the spectacles.
Normally, the spectacles frame is formed by a front part which is structured so as to support the two lenses, and is adapted to be arranged straddling the nose, at the height of the eyes; and by two lateral sidearms which protrude cantilevered from the front part of the spectacles frame, on opposite sides of the same, while remaining locally parallel and spaced apart and substantially perpendicular to the lying plane of the front part, so as to be able to rest on the ears of the person who wears the spectacles to give lateral stability to the front part.
More in detail, the proximal end of each lateral sidearm is usually fixed to the front part of the spectacles frame by a connection hinge of metal material, which allows the sidearm to rotate with respect to the front part about a reference axis that is locally substantially perpendicular to the longitudinal axis of the sidearm and also locally substantially parallel to the lying plane of the front part of the spectacles frame. The rotation axes of the two lateral sidearms are also substantially locally parallel and facing each other.
Each connection hinge, in particular, is composed of two anchoring elements in metal material, which are structured so as to be rigidly fixed one on the lateral side of the front part of the spectacles frame, and the other on the proximal end of the sidearm; and by a connection pin made of metal material, which is pass-through and axially rotatable within a series of pass-through holes especially made in the two anchoring elements, so as to allow the two anchoring elements to rotate one with respect to the other, about the longitudinal axis of the pin.
More in detail, in most of the spectacles-frame hinges currently on the market, the connection pin consists of a cylindrical shank screw, which has the shank end threaded so as to be screwed directly into the body of one of the two anchoring elements, and the remaining part of the shank perfectly smooth so as to allow the other anchoring element to rotate freely about the connection pin.
Although it is extremely simple and economical to produce, this type of spectacles hinge requires the user to periodically tighten the screw that serves as a connection pin, so as to ensure the correct long run operation of the hinge.
The rotation of the anchoring elements about the shank of the screw, in fact, tends to loosen the screw progressively up to cause the complete detachment of the shank from the corresponding anchoring element, with all the drawbacks that this entails on the functionality of the hinge.